Longitudinally flexible expandable stent

ABSTRACT

Segmented articulatable stent of open structure comprised of end-connected struts of first and second lengths making up first and second segments with angular interconnects between adjacent first and second segments.

[0001] This application is a Continuation-in-Part of application Ser.No. 08/511,076, filed Aug. 3, 1995, the disclosure of which is herebyincorporated by reference.

[0002] 1. Field of the Invention

[0003] This invention relates to an endoprosthesis device forimplantation within a body vessel, typically a blood vessel. Morespecifically, it relates to a tubular expandable stent of improvedlongitudinal flexibility.

[0004] 2. Background of the Invention

[0005] Stents are placed or implanted within a blood vessel for treatingstenoses, strictures or aneurysms therein. They are implanted toreinforce collapsing, partially occluded, weakened, or dilated sectionsof a blood vessel. They have also been implanted in the urinary tractand in bile ducts.

[0006] Typically, a stent will have an unexpanded (closed) diameter forplacement and an expanded (opened) diameter after placement in thevessel or the duct. Some stents are self-expanding and some are expandedmechanically with radial outward force from within the stent, as byinflation of a balloon.

[0007] An example of the latter type is shown in U.S. Pat. No. 4,733,665to Palmaz, which issued Mar. 29, 1988, and discloses a number of stentconfigurations for implantation with the aid of a catheter. The catheterincludes an arrangement wherein a balloon inside the stent is inflatedto expand the stent by plastically deforming it, after positioning itwithin a blood vessel.

[0008] A type of self-expanding stent is described in U.S. Pat. No.4,503,569 to Dotter which issued Mar. 12, 1985, and discloses a shapememory stent which expands to an implanted configuration with a changein temperature. Other types of self-expanding stents not made of shapememory material are also known.

[0009] This invention is directed to stents of all these types whenconfigured so as to be longitudinally flexible as described in detailhereinbelow. Flexibility is a desirable feature in a stent so as toconform to bends in a vessel. Such stents are known in the prior art.Examples are shown in U.S. Pat. No. 4,856,516 to Hillstead; U.S. Pat.No. 5,104,404 to Wolff; U.S. Pat. No. 4,994,071 to MacGregor; U.S. Pat.No. 5,102,417 to Palmaz; U.S. Pat. No. 5,195,984 to Schatz; U.S. Pat.No. 5,135,536 to Hillstead; U.S. Pat. 5,354,309 to Shepp-Pesch et al.;EPO Patent Application 0 540 290 A2 to Lau; EPO Patent Application No. 0364 787 B1 to Schatz, and PCT Application WO 94/17754 (also identifiedas German Patent Application 43 03 181).

[0010] Generally speaking, these kinds of stents are articulated and areusually formed of a plurality of aligned, expandable, relativelyinflexible, circular segments which are interconnected by flexibleelements to form a generally tubular body which is capable of a degreeof articulation or bending. Unfortunately, a problem with such stents isthat binding, overlapping or interference can occur between adjacentsegments on the inside of a bend due to the segments moving toward eachother and into contact or on the outside of a bend the segments can moveaway from each other, leaving large gaps. This can lead to impropervessel support, vessel trauma, flow disturbance, kinking, balloon burstduring expansion, and difficult recross for devices to be installedthrough already implanted devices and to unsupported regions of vessel.

[0011] A diamond configuration with diagonal connections between eachand every diamond of each segment is also known but such closedconfigurations lack flexibility.

[0012] It is an object of this invention to provide a longitudinallyflexible stent of open configuration that avoids these problems andexhibits improved flexibility (radially and longitudinally) in the stentbody segments thereof rather than in flexible joints between thesegments.

[0013] It is a further object of the present invention to provide astent that is flexible yet also allows for side branch access.

SUMMARY OF THE INVENTION

[0014] It is a goal of the present invention to provide a flexible stentformed of interconnected bands which provides for side branch access andwhich further avoids the problem of pinching or overlap between adjacentbands. Pinching or overlap is avoided where peaks and troughs ofadjacent bands are circumferentially displaced relative to each other.The stents of the present invention accomplish this goal by havingdifferent bands characterized by different wavelengths over the lengthof the stent and/or disposing the interconnecting members in such a waythat after expansion of the stent, the phase relationship betweenadjacent bands is altered with the peaks and troughs displacedcircumferentially relative to each other.

[0015] The inventive expandable stents are formed of a plurality ofinterconnected band-like elements characterized by alternating peaks andtroughs. The ends of the interconnecting members which join adjacentbands are circumferentially offset and optionally, longitudinallyoffset. Peaks and troughs in adjacent bands are circumferentially offsetas well so that the stent, in an expanded state, will have minimaloverlap of peaks and troughs.

[0016] To this end, the invention provides a tubular, flexible,expandable stent, comprising a plurality of undulating band-likeelements of a selected wavelength or wavelengths. The band-like elementshave peaks and troughs and are aligned on a common longitudinal axis todefine a generally tubular stent body. The peaks and troughs take agenerally longitudinal direction along the stent body. Adjacentband-like elements may be in phase or out of phase with each other. Theinventive stents further comprise a plurality of interconnectingelements having first ends and second ends. The first and second endsextend from adjacent band-like elements and are displaced from oneanother in a longitudinal direction and in a radial direction along thestent. Desirably, upon expansion of the stent, at least some of thepeaks and troughs of a given band-like element are displaced relative toeach other about the periphery of the stent to accommodate longitudinalflexing of the stent within the band-like elements and withoutinterference between adjacent band-like elements.

[0017] In one embodiment, two different types of band-like elements arepresent in the stent, first band-like elements with a first selectedwavelength and second band-like elements with a second selectedwavelength exceeding the first selected wavelength. The first and secondband-like elements preferably alternate over the length of the stent.Although the terminology of ‘first band-like element’ and ‘secondband-like element’ is used, it is not intended to convey the relativeorder of appearance of the elements in the inventive stents.

[0018] In another embodiment, two different types of band-like elementsare present, first and second band-like elements, each of which haspeaks and troughs. The first band-like elements have more peaks (ortroughs) than the second band-like elements. Similarly, the invention isalso directed to embodiments having first and second band-like elementswith peaks and troughs where the peaks (or troughs) of the firstband-like elements are spaced closer together than the peaks (ortroughs) of the second band-like elements.

[0019] In another embodiment in which band-like elements of only onewavelength are present, adjacent bands are about 180° out of phase withone another. Interconnecting elements extend at an oblique anglerelative to the longitudinal axis from a peak to a trough on an adjacentband.

[0020] In another embodiment in which band-like elements of only onewavelength are present, peaks from which interconnecting elementsemanate are elongated relative to the peaks which are not connected totroughs and similarly, the troughs from which interconnectors emanateare elongated relative to troughs which are not connected to peaks.Further, each interconnecting element extends from the side of a peak tothe side of a trough on an adjacent band.

[0021] In yet another embodiment in which band-like elements of only onewavelength are present, adjacent bands are about 90° out of phase withone another. Each interconnecting element extends between a peak and atrough and the ends of the interconnecting member are circumferentiallyoffset from one another and, optionally, longitudinally offset.

[0022] The invention further provides a tubular, flexible, expandablestent having a longitudinal axis, comprising one or more cylindricalshaped first segments having first struts, the first segment beingdefined by a member formed in an undulating pattern of interconnectedpaired first struts and in which adjacent pairs of first struts in agiven first segment are interconnected at opposite ends and one or morecylindrical shaped second segments defined by a member formed in anundulating pattern of interconnected paired second struts and in whichadjacent pairs of second struts in a given second segment areinterconnected at opposite ends. The first struts are shorter than thesecond struts. The first segments are formed of a number of first strutsand the second segments are formed of a number of second struts with thenumber of first struts in a first segment exceeding the number of secondstruts in a second segment. The first and second segments, present anddesirably alternating along the stent body, are aligned on a commonlongitudinal axis to define a generally tubular stent body. Adjacentfirst and second segments are connected by a plurality ofinterconnecting elements, each interconnecting element extending from anend of paired first struts on a first segment to an end of paired secondstruts on an adjacent second segment. The ends of interconnectingelements are circumferentially offset relative to each other, andoptionally, longitudinally offset. Desirably, upon expansion of thestent, the paired struts of the adjacent segments are displaced relativeto each other about the periphery of the stent body to accommodatelongitudinal flexing of the stent within the segments and withoutinterference between adjacent segments.

BRIEF DESCRIPTION OF THE DRAWINGS

[0023]FIG. 1a shows a band-like element used in the inventive stents.

[0024]FIG. 1b shows a schematic of a peak region which contains a doublepeak and a trough region containing a double trough.

[0025]FIG. 2 shows a flat view of a stent configuration according to theinvention.

[0026]FIG. 3 shows the pattern of FIG. 2 in a tubular stent.

[0027]FIG. 4a shows a flat view of a stent configuration according tothe invention.

[0028]FIG. 4b shows a flat view of a stent configuration according tothe invention.

[0029]Figure 5a shows a flat view of a stent configuration according tothe invention.

[0030]Figure 5b shows a flat view of a stent configuration according tothe invention.

[0031]FIG. 6 shows a flat view of a stent configuration according to theinvention.

[0032]FIG. 7 shows a flat view of a stent configuration according to theinvention.

[0033]FIG. 8 shows a flat view of a stent configuration according to theinvention.

[0034]FIG. 9 shows a flat view of a stent configuration according to theinvention.

[0035]FIG. 10 shows a flat view of a stent configuration according tothe invention.

[0036]FIG. 11 shows a flat view of a stent configuration according tothe invention.

[0037]FIG. 12 shows a flat view of a stent configuration according tothe invention.

[0038]FIG. 13 shows the pattern of FIG. 12 in a tubular stent.

[0039]FIG. 14 shows an expanded stent of the configuration shown in FIG.12.

[0040]FIG. 15 shows a flat view of an alternate stent configurationaccording to the invention.

DETAILED DESCRIPTION OF THE INVENTION

[0041] While this invention may be embodied in many different forms,there are described in detail herein specific preferred embodiments ofthe invention. This description is an exemplification of the principlesof the invention and is not intended to limit the invention to theparticular embodiments illustrated.

[0042] For the sake of consistency, the terms ‘peak’ and ‘trough’ shallbe defined with respect to the proximal and distal ends of the stent.Each of the stents has a proximal end 91 and a distal end 93 and alongitudinal axis 95, as seen in FIG. 1a. Peaks 36 are generally concaverelative to the proximal end of the stent and generally convex relativeto the distal end of the stent. Troughs 40, on the other hand, aregenerally convex relative to the proximal end of the stent and generallyconcave relative to the distal end of the stent. Notwithstanding thisdefinition, the term peak is also intended to extend to regions 48 thatare generally peak-like which may, nevertheless, contain trough-likeregions within the peak-like region as seen in FIG. 1b. Similarly theterm trough is also intended to extend to regions 52 that are generallytrough-like which may, nevertheless, contain peak-like regions withinthe trough-like region as seen in FIG. 1b.

[0043] Corresponding to each peak 36 is an inner diameter peak 38 wherethe inner diameter of the band-like element reaches its peak. The set ofpoints on a given band-like element which are distal to inner diameterpeak 38 is denoted peak region 48. Similarly, corresponding to eachtrough 40 is an inner diameter trough 42 where the inner diameter of theband-like element reaches its trough. The set of points on a givenband-like element which are proximal to inner diameter trough 42 isdenoted trough region 52. For the sake of clarity, unless otherwiseindicated, analogous portions of stents will be similarly labeled, usingthree digit reference numerals to distinguish among the variousembodiments shown.

[0044] Also included within this definition of peak regions and troughregions are peak regions which are comprised of multiple peaks as wellas trough regions which are comprised of multiple troughs such as thoseshown schematically in FIG. 1b. Peak 36 is seen to consist of twosub-peaks 36 a, b and trough 40 is similarly seen to consist of twosub-troughs 40 a, b. In the case of peaks containing sub-peak andtroughs containing sub-troughs, the peak region 48 includes all of thepoints along the band-like element between the sub-peaks that make upthe peak and similarly, the trough region 52 includes all of the pointsalong the band-like element between the sub-troughs that make up thetrough.

[0045] The inventive stents may incorporate one or more bands of achosen wavelength. In some embodiments, the inventive stents include oneor more small amplitude, short wavelength bands to provide forflexibility and one or more large amplitude, long wavelength bands togive side branch access or to provide for sections of alternativestrengths such as soft and/or stiff sections.

[0046] Turning to the Figures, FIG. 2 shows a flat view of a stentconfiguration and FIG. 3 shows the stent of FIG. 2 in tubular form. Thatis, the stent is shown for clarity in FIG. 2 in the flat and may be madefrom a flat pattern 110 (FIG. 2) which is formed into a tubular shape byrolling the pattern so as to bring edges 112 and 114 together (FIG. 2).The edges may then joined as by welding or the like to provide acylindrical configuration such as that shown generally at 115 in FIG. 3.

[0047] A more preferred method of manufacture begins with a thin walledtube which is then laser cut to provide the desired configuration. Itmay also be chemically etched or EDM'd (electrical discharge machined)to form an appropriate configuration.

[0048] The configuration can be seen in these Figures to be made up ofone or more spaced first band-like elements 120. First band-likeelements have a generally serpentine configuration to provide continuouswaves to the first band-like elements. The waves are characterized by aplurality of peaks 124 and troughs 128 taking a generally longitudinaldirection along the cylinder such that the waves in first band-likeelements 120 open as the stent is expanded from an unexpanded statehaving a first diameter to an expanded state having a second diameter.

[0049] The stent further comprises a plurality of spaced secondband-like elements 132 having a generally serpentine configuration toprovide continuous waves to the second band-like elements. The waves arecharacterized by a plurality of peaks 136 and troughs 140 taking agenerally longitudinal direction along the cylinder such that the wavesin the second band-like elements open as the stent is expanded from anunexpanded state having a first diameter to an expanded state having asecond diameter. First and second band-like elements are characterizedby respective wavelengths and amplitudes with the wavelength andamplitude of the second band-like elements exceeding the wavelength andamplitude of the first band-like elements.

[0050] Adjacent first band-like elements 120 and second band-likeelements 132 are interconnected via a plurality of interconnectingelements 144. The ends of interconnecting element are circumferentiallyoffset from each other.

[0051] In an embodiment, as shown in FIGS. 2 and 3, first band-likeelements 120 and second band-like elements 132 alternate over the lengthof the stent. Optionally, as shown in FIGS. 2 and 3, each end 152 of thestent may terminate in a first band-like element. The invention also,however, contemplates each end terminating in a second band-likeelement, or further, one end terminating in a first band-like elementand the other end terminating in a second band-like element.

[0052] While a minimum of one connecting element is required to joinadjacent band-like elements, two or more interconnecting elements arepreferred. In one embodiment, as shown in FIGS. 2 and 3, adjacent firstand second band-like elements 120 and 132 are connected with threeinterconnecting elements 144. Further, in one embodiment, adjacentinterconnecting elements 144 extending from peaks 136 on a firstband-like element 120 are spaced five peaks apart on the first band-likeelement while adjacent interconnecting elements 144 extending fromtroughs 140 on a second band-like element 132 are spaced three troughsapart on the second band-like element.

[0053] It is a further feature of the present invention that peaks 124on first band-like elements 120 are circumferentially displaced on theperiphery of the stent from troughs 140 on adjacent second band-likeelements 132. It is desirable that peaks and troughs be displaced in theexpanded state of the stent to minimize the possibility of pinching oroverlap between adjacent band-like elements.

[0054] Although the stent of FIG. 2 is comprised of two differentwavelength band-like elements, the invention contemplates stents with aplurality of different wavelength band-like elements. As such, otherstents may have three, four or more different wavelength band-likeelements.

[0055] In another embodiment, the inventive stent is comprised ofband-like elements of a single wavelength, interconnected byinterconnecting elements. Turning to FIGS. 4a and 4 b, band-likeelements 220 a, b are interconnected by interconnecting elements 244 a,b. Adjacent band-like elements 220 a, b are 180° out of phase with oneanother. In the compressed state, the band-like elements consist of aplurality of peaks 236 a, b and troughs 240 a, b. Peak region 248 a, band trough region 252 a, b have been shaded in one instance forillustrative purposes.

[0056] In the embodiment shown in FIG. 4a, each interconnecting element244 a extends between a peak region 248 a and a trough region 252 a.Rectilinear interconnecting elements 244 a consist of a first shank 280a, a second shank 284 a and a link 288 a disposed in-between the firstand second shanks 280 a and 284 a. First shank 280 a extends in alongitudinal direction from peak region 248 a and is substantiallyperpendicular to link 288 a. Second shank 284 a extends in alongitudinal direction from trough region 252 a and is perpendicular tolink 288 a.

[0057] In the embodiment shown in FIG. 4b, the stent differs from theembodiment of FIG. 4a in that interconnecting element 244 b extendingbetween a peak region 248 b and a trough region 252 b is curvilinearrather than rectilinear.

[0058] In both FIGS. 4a and 4 b, the interconnecting elements are seento emanate from the middle of the peak and trough regions.

[0059] In another embodiment, as shown in FIG. 5a, the inventive stentis comprised of band-like elements 320 a of a single wavelength,interconnected by interconnecting elements 344 a. Adjacent band-likeelements 320 a are 180° out of phase with one another. The band-likeelements consist of a plurality of peaks 336 a and troughs 340 a.Interconnecting elements 344 a extend between a peak region 348 a and atrough region 352 a. The peak regions 348 a and trough regions 352 afrom which interconnecting elements 344 a emanate on a given band-likeelement 320 a are seen to extend longitudinally beyond adjacent peakregions 348 a′ and trough regions 352 a′ from which no interconnectingelements extend. The extension is such that at least a portion of peakregions 348 a overlap longitudinally along the stent with at least aportion of trough region 352 a on an adjacent band-like element 320 a.Of course, the overlap is limited to the longitudinal direction and notto the circumferential direction.

[0060] In another embodiment, as shown in FIG. 5b, interconnectingelements 344 b extend between peak region 348 b and a second closesttrough region 352 b on an adjacent band-like element. Interconnectingelements 344 b are seen to be perpendicular to the longitudinal axis. Asin the stent of FIG. 5a, peak regions 348 b from which interconnectingelements 344 b extend and trough regions 352 b from whichinterconnecting elements 344 b extend may extend beyond adjacent peakregions 348 b′ and trough regions 352 b′ from which no interconnectingelements 344 b emanates.

[0061] In another embodiment, as shown in FIG. 6, adjacent band-likeelements 420 are in phase with each other. As in previous Figs,band-like elements 420 are of a single wavelength, interconnected byinterconnecting elements 444. The band-like elements consist of aplurality of peaks 436 and troughs 440. Interconnecting elements 444extend at an oblique angle relative to the longitudinal axis of thestent between a peak region 448 and a trough region 452. As such, endsof interconnecting elements 444 are circumferentially offset relative toeach other. The exact angle will, of course, depend on the region fromwhich the interconnecting elements extend, as well as on whetherinterconnecting elements interconnect nearest peaks and troughs, nextnearest peaks and troughs or peaks and troughs that are furtherseparated.

[0062] In FIGS. 5a, 5 b and 6, the interconnecting elements are seen toemanate from the sides of the peak and trough regions.

[0063] Although for the embodiments of FIGS. 1-6, the interconnectingelements extend from peak regions on band-like elements to troughregions on adjacent band-like elements, the invention furthercontemplates interconnecting elements extending from a position betweena peak region and an adjacent trough region on a band-like element to aposition intermediate a trough region and a peak region on an adjacentsecond band-like element as in FIG. 7.

[0064] In the embodiment of FIG. 7, interconnecting elements are seen toextend from a region between the peak region and the trough region on aband-like element. The stent is formed of adjacent band-like elements520 which are 180° degrees out of phase with one another.Interconnecting elements 544 extend from a region intermediate a peakregion 548 and a trough region 552 on a band-like element to a regionintermediate a peak region 548 and a trough region 552 on an adjacentband-like element. Interconnecting elements 544 consist of a first shank560, a second shank 564, and an intermediate member 568 disposedin-between first and second shanks 560 and 564. First shank 560 andsecond shank 564 are substantially perpendicular to intermediate member568 which extends in the longitudinal direction. Although not depicted,the region from which interconnecting elements 544 emanate may be midwaybetween peaks and troughs.

[0065] The embodiment of FIG. 7 also differs from the embodiments ofFIGS. 2-6 in the orientation of the interconnecting elements. Whereasthe interconnecting elements in FIGS. 2-6 are all similarly oriented, inthe embodiment of FIG. 7, the orientation of interconnecting elementsalternates between adjacent pairs of adjacent band-like elements.Specifically, second shanks 564′ of interconnecting elements 544′ areseen to be displaced in a clockwise circumferential direction along thestent relative to first shanks 560′, and seconds shank 564″ ofinterconnecting elements 544″ are seen to be displaced in acounterclockwise circumferential direction along the stent relative towhile first shank 560″.

[0066] This feature is also seen in the embodiment of FIG. 8 in whichadjacent in-phase band-like elements 620 are interconnected byinterconnecting elements 644. Interconnecting elements 644 extend at anoblique angle relative to the longitudinal axis of the stent between apeak region 648 and a trough region 652. As in FIG. 7, the orientationof interconnecting elements alternates between adjacent pairs ofadjacent band-like elements. Specifically, the distal ends ofinterconnecting elements 644′ are seen to be oriented in acounterclockwise circumferential direction along the stent relative tothe proximal end of the interconnecting elements while the distal endsof interconnecting elements 644″ are seen to be displaced in a clockwisecircumferential direction along the stent relative to the proximal ends.

[0067] Although in the embodiments of FIGS. 2-8, adjacent bands areconnected by five interconnecting elements, additional or fewerinterconnecting elements may be used. Further, while interconnectingelements are shown spaced three peaks apart and three troughs apart,other separations are contemplated as well.

[0068] In the embodiment of FIG. 9, each band-like element 720 is seento comprise peaks 736 of more than one amplitude and troughs 740 of morethan one amplitude . Large amplitude peaks 736 a and small amplitudepeaks 736 b alternate as do large amplitude troughs 740 a and smallamplitude troughs 740 b. As in the previous embodiments, theinterconnecting elements are oriented at an oblique angle relative tothe longitudinal axis 795 of the stent. More generally, the invention isdirected at stents comprising band-like elements whose amplitude variesalong the band-like element.

[0069] In another embodiment of the invention, as shown in FIG. 10, eachband-like element 820 is seen to comprise peaks 836 of more than oneamplitude and troughs 840 of more than one amplitude, however, peaks ofthe same amplitude are grouped together within a band-like element asare troughs of the same amplitude. It is further noted that in theembodiment of FIG. 10, the location of a group of peaks of givenamplitude in a band-like element varies circumferentially along thelength of the stent. Interconnecting elements 844 connect peaks 836 andtroughs 840 in adjacent band-like elements 820. Where several peaks ofdifferent amplitudes are present in a band-like element, the inventionfurther contemplates the possibility of interconnecting elementsextending from the large peaks 836 a to large troughs 840 a as in FIG. 9as well as the possibility of interconnecting elements extending fromlarge peaks to small troughs or from small peaks 836 b to large troughs840 a as in FIG. 10. Further, the interconnecting elements between anytwo adjacent band-like elements may be of different lengths from oneanother as seen in FIG. 10 and commence at different longitudinalpositions within a band-like element and terminate at differentlongitudinal positions within a band-like element. Interconnectingelement 844 a is seen to be longer than interconnecting element 844 b.As in the previous embodiments, the interconnecting elements areoriented at an oblique angle relative to the longitudinal axis 895 ofthe stent. In the embodiment of FIG. 10, interconnecting element 844 ais seen to be oriented at a smaller oblique angle relative to thelongitudinal axis of the stent than interconnecting element 844 b. As isapparent from FIG. 10, the invention is also directed to stentscomprised of band-like elements whose wavelength varies along a givenband-like element. Region 898 and region 899 of band-like element arecharacterized by different wavelengths.

[0070] It is also noted that in the embodiment of FIG. 10, all of thetroughs 840 a, b in a given band-like element 820 are alignedlongitudinally along the stent and differ only in their circumferentialposition along the stent.

[0071] It is further noted in the embodiment of FIG. 10, the stentcomprises a first group of interconnecting elements 844 a and a secondgroup of interconnecting elements 844 b. The interconnecting elements ofthe first group are all parallel to one another and disposed at adifferent oblique angle relative to the longitudinal axis than themembers of the second group which are all parallel to one another. Assuch, the invention contemplates stents having several different groupsof obliquely disposed interconnecting elements where the oblique anglediffers from group to group.

[0072] In another embodiment of the invention, as shown in FIG. 11, eachband-like element 920 is seen to comprise peaks 936 a, b of differentamplitudes and troughs 940 of different amplitudes, however, peaks ofthe same amplitude are grouped together within a band-like element asare troughs of the same amplitude. It is further noted that in theembodiment of FIG. 11 the location of groups of peaks of given amplitudein a band-like element varies circumferentially along the length of thestent. Interconnecting elements 944 connect large amplitude peaks 936 aand small amplitude troughs 940 b in adjacent band-like elements 920.Similarly, interconnecting elements 944 also connect small amplitudepeaks 936 b and large amplitude troughs 940 a.

[0073] The invention also contemplates stents similar to that shown inFIG. 11 in which interconnecting elements extend from large peaks 936 ato large troughs 940 a, as in FIG. 9. Similarly, interconnectingelements may extend from small peaks 936 b to small troughs 940 b.

[0074] Further, the interconnecting elements between any two adjacentband-like elements may be of different lengths from one another anddisposed at different oblique angles.

[0075] As is apparent from FIG. 11, the invention is also directed tostents comprised of band-like elements whose wavelength varies along agiven band-like element. Region 998 and region 999 of band-like element920 are characterized by different wavelengths.

[0076] It is also noted that in the embodiment of FIG. 11 the largeamplitude portions 999 of band-like element 920 are symmetricallydisposed about the center 1001 of the band-like element as are the smallamplitude portions 998. The center 1001 of the band-like element isdefined as a ring that runs along a path that is midway between thelarge peaks 936 a and large troughs 940 a of the band-like element. Thisfeature may also be seen in the embodiment of FIG. 9.

[0077] The invention is also directed to a tubular, flexible, expandablestent having a longitudinal axis, comprising one or more cylindricalshaped first segments. Cylindrical shaped first segments 20 as seen inFIG. 1, have first struts 23 having first 25 and second 27 ends. Firstsegments 20 are defined by a member formed in an undulating pattern ofinterconnected paired first struts 23, in which adjacent pairs of firststruts 29′ and 29″ in a given first segment 20 are interconnected atopposite ends 31′ and 31″, respectively. Adjacent segments areinterconnected.

[0078] The stent may be seen more clearly in FIGS. 2-8. As shown, thestent of FIG. 3, in addition to comprising first segments 120 which aredefined by an undulating pattern of interconnected paired first struts123 in which adjacent pairs of first struts 129′ and 129″ in a givenfirst segment 120 are interconnected at opposite ends 131′ and 131″,respectively, the stent further comprises one or more cylindrical shapedsecond segments 132, each second segment being defined by a memberformed in an undulating pattern of interconnected paired second struts135 and in which adjacent pairs of second struts 137′ and 137″ in agiven second segment 132 are interconnected at opposite ends 139′ and139″, respectively. First struts 123 are shorter than second struts 135.First segments 120 are formed of a number of first struts 123 and secondsegments 132 formed of a number of second struts 135, the number offirst struts in a first segment exceeding the number of second struts ina second segment. First and second segments 120 and 132 are aligned on acommon longitudinal axis 195 to define a generally tubular stent body,shown generally at 115. First and second segments 120 and 132 alternatealong the stent body. Adjacent first and second segments 120 and 132 areconnected by a plurality of interconnecting elements 144. Eachinterconnecting element 144 extends from an end 131″ of paired firststruts on a first segment 120 to an end 139″ of paired second struts onan adjacent second segment 132. The ends of interconnecting elements 144are circumferentially offset relative to each other.

[0079] Desirably, upon expansion of stent 115, paired struts 129″ and137″ of adjacent segments 120 and 132 are displaced relative to eachother about the periphery of the stent body to accommodate longitudinalflexing of the stent within the segments and without interferencebetween adjacent segments.

[0080] In the embodiments as shown in FIGS. 4a, b, cylindrical shapedsegments 220 a, b are formed of interconnected struts 223 a, b havingfirst 225 and second 227 ends. Adjacent pairs of struts 229 a, b′ and229 a, b ″ in a given segment 220 a, b are interconnected at oppositeends 231 a, b′ and 231 a, b″, respectively. Adjacent segments areconnected by a plurality of interconnecting elements 244 a, b. Eachinterconnecting element 244 a, b extends from an end of paired struts231 a, b″ on a segment to an end of paired struts 231 a, b′ on anadjacent segment. First end 245 a, b and second end 247 a, b ofinterconnecting elements 244 a, b are seen to be circumferentiallydisplaced along the stent.

[0081] Similar structure, denoted by similar reference numerals may befound in the stents of FIGS. 5a, b, and 6-8.

[0082] In particular, in the embodiment as shown in FIG. 8, cylindricalshaped segments 620 are formed of interconnected struts 623, havingfirst 625 and second 627 ends. Segments 620 are defined by a memberformed in an undulating pattern of interconnected paired struts 623 inwhich adjacent pairs of struts 629′ and 629″ in a given segment 620 areinterconnected at opposite ends 631′ and 631″, respectively. Segments620 are aligned on a common longitudinal axis 695 to define a generallytubular stent body. Adjacent segments are connected by a plurality ofinterconnecting elements 644 (and 644′) having first 645 (645′) andsecond 647 (647′) ends, each interconnecting element 644 (644′)extending from an end of paired struts 631″ on a segment to an end ofpaired struts 631′ on an adjacent segment. First end 645 (645′) andsecond end 647 (647″) are seen to be circumferentially displaced alongthe stent.

[0083] Additional embodiment of the stents are shown in FIGS. 12-15.FIG. 12 and FIG. 13 show a fragmentary flat view of an unexpanded stentconfiguration and the actual tubular stent (unexpanded), respectively.That is, the stent is shown for clarity in FIG. 12 in the flat and maybe made from a flat pattern 1110 (FIG. 12) which is formed into atubular shape by rolling the pattern so as to bring edges 1112 and 1114together (FIG. 12). The edges may then joined as by welding or the liketo provide a configuration such as that shown in FIG. 13.

[0084] The configuration can be seen in these Figures to be made up of aplurality of adjacent segments generally indicated at 1116, each ofwhich is formed in an undulating flexible pattern of substantiallyparallel struts 1118. Pairs of struts are interconnected at alternatingend portions 1119 a and 1119 b. As is seen in FIG. 12, theinterconnecting end portions 1119 b of one segment are positionedopposite interconnecting end portions 1119 a of adjacent segments. Theend portions as shown are generally elliptical but may be rounded orsquare or pointed or the like. Any configuration of end portions isacceptable so long as it provides an undulating pattern, as shown. Whenthe flat form 1110 is formed into an unexpanded tube as shown in FIG.13, the segments are cylindrical but the end portions 1119 of adjacentsegments remain in an opposed position relative to each other.

[0085] A more preferred method of manufacture begins with a thin walledtube which is then laser cut to provide the desired configuration. Itmay also be chemically etched or EDM'd (electrical discharge machined)to form an appropriate configuration.

[0086] Interconnecting elements 1120 extend from one end portion 1119 ofone segment 1116 to another end portion 1119 of another adjacent segment1116 but not to an oppositely positioned end portion 1119 of an adjacentsegment 1116. There are at least three struts included between thepoints on each side of a segment 1116 at which an interconnectingelement 1120 contacts an end portion 1119. This results in theinterconnecting elements 1120 extending in an angular direction betweensegments around the periphery of the tubular stent. Interconnectingelements 1120 are preferably of the same length but may vary from onesegment to the other. Also, the diagonal direction may reverse from onesegment to another extending upwardly in one case and downwardly inanother, although all connecting elements between any pair of segmentsare substantially parallel. FIG. 12, for example shows them extendingdownwardly, right to left. Upwardly would extend up left to right inthis configuration.

[0087] As a result of this angular extension of the interconnectingelements 1120 between adjacent segments and loops, upon expansion of thestent as seen in FIG. 14, the closest adjacent end portions 1119 betweensegments 1116 are displaced from each other and are no longer oppositeeach other so as to minimize the possibility of binding or overlappingbetween segments, i.e., pinching.

[0088] The number of interconnecting elements 1120 may vary depending oncircumstances in any particular instance. Three per segment aresatisfactory for the configuration shown and at least three will be usedtypically.

[0089] The alternate design shown in FIG. 15 includes longer struts 1118a in the two end segments 1116 a than in the intermediate segments 1116.This allows the end segments (1116 a) to have less compressionresistance than the intermediate segments (1116), providing a moregradual transition from the native vessel to the support structure ofthe stent. Otherwise, the configuration is the same as that shown inFIG. 12.

[0090] As indicated in the Figures, the invention contemplates avariation of interconnecting element shapes ranging from rectilinear tocurvilinear. The invention further contemplates embodiments in which allinterconnecting elements are similarly oriented as well as embodimentsin which adjacent sets of interconnecting elements extending betweenadjacent pairs of segments are oppositely oriented (e.g., FIGS. 7 and8). The invention also contemplates the use of interconnecting elementswhich extend from a range of positions along the segments, ranging fromvarious positions in the area in which paired struts are interconnectedto other positions along the struts.

[0091] The invention also contemplates the possibility ofinterconnecting elements extending at an oblique angle relative to thelongitudinal axis of the stent and connecting adjacent peaks and troughson adjacent segments as well as peaks and troughs on adjacent segmentswhich are separated by one or more peaks and/or troughs.

[0092] The invention also contemplates reversing the orientation ofinterconnecting elements as shown in FIGS. 7 and 8.

[0093] Finally, there are preferably at least three interconnectingelements joining adjacent first and second segments although fewer oradditional interconnecting elements are also contemplated.

[0094] It is understood that the peaks and troughs of the presentinvention need not be rounded, as shown in the Figures. The peaks andtroughs may be bulbous, triangular, square, pointed, or otherwise formedof interconnected straight sections.

[0095] As already indicated, this invention is applicable toself-expanding configurations, mechanically expandable configurationsand to a wide variety of materials, including both metal and plastic andany other material capable of functioning as an expandable stent. Forexample, the stent may be of metal wire or ribbon such as tantalum,stainless steel or the like. It may be thin-walled. It may be of shapememory alloy such as Nitinol or the like, etc. The interconnectingelements may be formed integrally with the band-like elements (orsegments) or may be bonded thereto via such methods as adhesive bonding,welding or any other known method of bonding.

[0096] The above Examples and disclosure are intended to be illustrativeand not exhaustive. These examples and this description will suggestmany variations and alternatives to one of ordinary skill in this art.All these alternatives and variations are intended to be included withinthe scope of the attached claims. Those familiar with the art mayrecognize other equivalents to the specific embodiments described hereinwhich equivalents are also intended to be encompassed by the claimsattached hereto.

1-37. (Canceled)
 38. A stent for holding open a blood vessel comprising:a. a first loop containing section, the first loop containing sectionarranged generally in the circumferential direction, the loops in saidfirst loop containing section occurring at a first frequency; b. asecond loop containing section, the second loop containing sectionarranged generally in the circumferential direction, the loops in saidsecond loop containing section also occurring at said first frequency;and c. a third loop containing section the third loop containingsection, the loops in said third loop containing section occurring at asecond frequency that is higher than said first frequency, disposed inthe generally circumferential space between said first and second loopcontaining sections and alternately joined to said first and second loopcontaining sections, d. wherein the loops in said first, second andthird loop containing sections are disposed and adapted to cooperate sothat, when the expanded stent is in a curved lumen, cells on the outsideof the curve open in length, but narrow circumferentially whereas cellson the inside of the curve shorten in length but widencircumferentially, and e. the third loop containing section compensatesfor foreshortening of the first and second loop containing sections whenthe stent is expanded such that the widths of the first and second loopcontaining sections are smaller expanded than compressed, and the widthof the third loop containing section is greater expanded thancompressed.
 39. A stent according to claim 38 wherein compensation,which occurs when cells on the outside of the curve open in length, butnarrow circumferentially and cells on the inside of the curve shorten inlength but widen circumferentially, results in a more constant densityof stent element area between the inside and the outside of the curvethan if the cells on the outside only lengthened and cells on the insideonly shortened.
 40. A stent according to claim 38 wherein compensation,which occurs when cells on the outside of the curve open in length, butnarrow circumferentially and cells on the inside of the curve shorten inlength but widen circumferentially, results in a more constant stentcell area between the inside and the outside of the curve than if thecells on the outside only lengthened and cells on the inside onlyshortened.
 41. A stent for widening a vessel in the human bodycomprising: a. a plurality of first circumferential bands containing apattern of loops at a first frequency; b. a plurality of secondcircumferential bands containing a pattern of loops at a secondfrequency higher than said first frequency, alternating with said firstcircumferential bands and periodically coupled thereto to form cells, c.wherein loops in said bands are disposed and adapted to cooperate sothat, when the expanded stent is in a curved lumen, cells on the outsideof the curve open in length, but narrow circumferentially whereas cellson the inside of the curve shorten in length but widencircumferentially, and d. the second circumferential bands compensatefor foreshortening of the first circumferential bands when the stent isexpanded such that the widths of the first circumferential bands aresmaller expanded than compressed, and the widths of the secondcircumferential bands are greater expanded than compressed.
 42. A stentaccording to claim 41 wherein compensation, which occurs when cells onthe outside of the curve open in length, but narrow circumferentiallyand cells on the inside of the curve shorten in length but widencircumferentially, results in a more constant density of stent elementarea between the inside and the outside of the curve than if the cellson the outside only lengthened and cells on the inside only shortened.43. A stent according to claim 40 wherein compensation, which occurswhen cells on the outside of the curve open in length, but narrowcircumferentially and cells on the inside of the curve shorten in lengthbut widen circumferentially, results in a more constant stent cell areabetween the inside and the outside of the curve than if the cells on theoutside only lengthened and cells on the inside only shortened.
 44. Astent for holding open a blood vessel formed of a plurality oftriangular cells, each triangular cell comprising: a. a first loopcontaining section, the first loop containing section arranged generallyin the circumferential direction; b. a second loop containing sectionjoined to the first loop containing section at a first junction point;and c. a third loop containing section joined to the first loopcontaining section at a second junction point and joined to the secondloop containing section at a third junction point, d. wherein loops insaid cells are disposed and adapted to cooperate so that, when theexpanded stent is in a curved vessel, cells on the outside of the curveopen in length, but narrow circumferentially whereas cells on the insideof the curve shorten in length but widen circumferentially, and e. thethird loop containing section compensates for foreshortening of thefirst and second loop containing sections when the stent is expandedsuch that the widths of the first and second loop containing sectionsare smaller expanded than compressed, and the width of the third loopcontaining section is greater expanded than compressed.
 45. A stentaccording to claim 44 wherein compensation, which occurs when cells onthe outside of the curve open in length, but narrow circumferentiallyand cells on the inside of the curve shorten in length but widencircumferentially, results in a more constant density of stent elementarea between the inside and the outside of the curve than if the cellson the outside only lengthened and cells on the inside only shortened.46. A stent according to claim 44 wherein compensation, which occurswhen cells on the outside of the curve open in length, but narrowcircumferentially and cells on the inside of the curve shorten in lengthbut widen circumferentially, results in a more constant stent cell areabetween the inside and the outside of the curve than if the cells on theoutside only lengthened and cells on the inside only shortened.
 47. Astent for widening a vessel in the human body comprising: a. a pluralityof first meander patterns; b. a plurality of second meander patternsintertwined with the first meander patterns to form triangular cells,said first meander patterns and said second meander patterns disposedand adapted to cooperate so that after expansion of said stent, whensaid stent is dispose in a curved vessel, cells on the outside of thecurve open in length, but narrow circumferentially whereas cells on theinside of the curve shorten in length but widen circumferentially, andc. the second meander patterns compensate for foreshortening of thefirst meander patterns when the stent is expanded such that the widthsof the first meander patterns are smaller expanded than compressed, andthe width of the second meander patterns are greater expanded thancompressed.
 48. A stent according to claim 47 wherein compensation,which occurs when cells on the outside of the curve open in length, butnarrow circumferentially and cells on the inside of the curve shorten inlength but widen circumferentially, results in a more constant densityof stent element area between the inside and the outside of the curvethan if the cells on the outside only lengthened and cells on the insideonly shortened.
 49. A stent according to claim 47 wherein compensation,which occurs when cells on the outside of the curve open in length, butnarrow circumferentially and cells on the inside of the curve shorten inlength but widen circumferentially, results in a more constant stentcell area between the inside and the outside of the curve than if thecells on the outside only lengthened and cells on the inside onlyshortened.
 50. A multicellular stent for holding open a lumen,comprising: a. a plurality of even and odd vertical meander patterns,the odd vertical meander patterns being located between every two evenvertical meander patterns and being out of phase with the even verticalmeander patterns, b. a plurality of even and odd horizontal meanderpatterns, the odd horizontal meander patterns being located betweenevery two even horizontal meander patterns, c. wherein the verticalmeander patterns are intertwined with the horizontal meander patterns toform a plurality of triangular cells, d. wherein said horizontal meanderpatterns and said vertical meander patterns are disposed and adapted tocooperate so that after expansion of said stent, when said stent isdisposed in a curved lumen, cells on the outside of the curve open inlength, but narrow circumferentially whereas cells on the inside of thecurve shorten in length but widen circumferentially, and e. saidhorizontal meander patterns and said vertical meander patterns form ahigh and a low frequency loop sections, wherein the high frequency loopsection compensates for foreshortening of the low frequency loop sectionwhen the stent is expanded such that width of the low frequency loopsection is smaller when expanded than compressed and width of the higherfrequency loop section is larger when expanded than compressed.
 51. Astent according to claim 50 wherein compensation, which occurs whencells on the outside of the curve open in length, but narrowcircumferentially and cells on the inside of the curve shorten in lengthbut widen circumferentially, results in a more constant density of stentelement area between the inside and the outside of the curve than if thecells on the outside only lengthened and cells on the inside onlyshortened.
 52. A stent according to claim 50 wherein compensation, whichoccurs when cells on the outside of the curve open in length, but narrowcircumferentially and cells on the inside of the curve shorten in lengthbut widen circumferentially, results in a more constant stent cell areabetween the inside and the outside of the curve than if the cells on theoutside only lengthened and cells on the inside only shortened.
 53. Anexpandable stent comprising a plurality of enclosed flexible spaces,each of the plurality of enclosed flexible spaces including: a) a firstmember having a first end and a second end; b) a second member having afirst end and a second end; c) a third member having a first end and asecond end; d) a fourth member having a first end and a second end; thefirst end of the first member communicating with the first end of thesecond member, the second end of the second member communicating withthe second end of the third member, and the first end of the thirdmember communicating with the first end of the fourth member; e) thefirst member and the second member with the curved portion at their endsforming a first loop; f) the third member and the fourth member with thecurved portion at their ends forming a second loop; g) a fifth memberhaving a first end and a second end; h) a sixth member having a firstend and a second end; i) a seventh member having a first end and asecond end; j) an eighth member having a first end and a second end; k)a ninth member having a first end and a second end; and l) a tenthmember having a first end and a second end, the first end of the fifthmember communicating with the second end of the first member, the secondend of the fifth member communicating with the second end of the sixthmember, the first end of the sixth member communicating with the firstend of the seventh member, the second end of the seventh membercommunicating with the second end of the eighth member, the first end ofthe eighth member communicating with the first end of the ninth member,the second end of the ninth member communicating with the second end ofthe tenth member, and the first end of the of the tenth membercommunicating with the second end of the fourth member; m) the fifthmember and the sixth member with the curved portion at their endsforming a third loop; n) the seventh member and the eighth member withthe curved portion at their ends forming a fourth loop; and o) the ninthmember and the tenth member with the curved portion at their endsforming a fifth loop, wherein, when the expanded stent is in a curvedlumen, cells on the outside of the curve at communication points of thefirst and fifth and fourth and tenth members, the cell opens upincreasing the length of the cell and at each of the first through fifthloops, the adjoining members come closer to each other, to cause thecell to become narrower circumferentially and compensating for theincrease in length, whereas cells on the outside of the curve atcommunication points of the first and fifth and fourth and tenthmembers, the cell closes down decreasing the length of the cell and ateach of the first through fifth loops, the adjoining members move apart,to cause the cell to become wider circumferentially and compensate forthe decrease in length, and the fifth through tenth members compensatefor foreshortening of the first through fourth members when the stent isexpanded such that width of the first through fourth members is smallerwhen expanded than compressed and width of the fifth through tenthmembers is larger when expanded than compressed.
 54. A stent accordingto claim 53 wherein the compensation which occurs on the outside of thecurve and on the inside of the curve results in a more constant densityof stent element area between the inside and the outside of the curvethan if the cells on the outside only lengthened and cells on the insideonly shortened.
 55. A stent according to claim 53 wherein thecompensation which occurs on the outside of the curve and on the insideof the curve results in a more constant stent area between the insideand the outside of the curve than if the cells on the outside onlylengthened and cells on the inside only shortened.